Method of supplying carbon dioxide for aiding the growth of plants



J, C. MINOR May 9, 1933.

METHOD OF SUPPLYING CARBON DIOXIDE FOR AIDING THE GROWTH OF PLANTS FiledMay l2, 1931 s dwf.

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Patented May 9, 1933 UNITED STATES PATENT oFFlcE JOHN C. MINOR, OF NEWCANAAN, CONNECTICUT; ASSIGNOR TO WILLIAM WHABTON JB. d: COMPANY,INCORPORATED, OF EASTON, PENNSYLVANIA., A CORPORATION OIE' PENNSYLVANIAMETHOD OF SUPPLYING CARBON DIOXIDE FOB AIDING THE GROWTH OF PLANTSApplication led May 12, 1931. Serial No. 536,796.

This invention relates to methods of enriching the carbon dioxidecontent of the atmosphere in proximity to growing plants to increase therate of growth of the latter.

The invention aims to provide a simple and highly efficient method ofsupplying the carbon dioxide to such atmosphere, especially in hothousesor enclosed spaces, where wind will not blow the carbon dioxide away asfast as it is liberated.

The ideal method would beto have the desired high carbon dioxideatmosphere only around the leaves of the plants to reduce the wastage ofcarbon dioxide to a minimum. I have found that these ideal conditionsmay be approached by introducing, preferably at a point or pointsashortvdistance above the top o f the foliage, gas high in carbon dioxideand at considerably lowerltemperature than the average atmospherictempera- Carbon dioxide is heavier than air. Further, a cold gas isheavier than the same gas at a higher temperature. Hence, cold carbondioxide gas, or gas high in carbon dioxide, when liberated above thefoliage will fall and in so'falling spread over and between the leavesof the plants and produce a layer of air relatively high in carbondioxide throughout the lower part of the hothouse. In this way thecarbon dioxide content of the atmosphere between and around the foliagemay be raised to a desired percentage, desirably about 0.3% or more,without raising the carbon dioxide content at higher levels to the samedegree.

The invention comprises a method of so supplying the cold carbon dioxidegas, or gas high in carbon dioxide, by allowlng solid carbon dioxide tovaporize under atmospheric pressure in suitable containers open to theatmosphere. The rate of vaporization is determined by the rate ofabsorption of external heat by the container and its contents, and maybe predetermined by the form, size and construction of thecontainer. l

Solid carbon dioxide has several advantages over liquid carbon dioxideas a source of gaseous carbon dioxide. It is much more easily handled.It can be cut or broken into lumps of the desired size, and these lumpscan be readily inserted .into the containers. Liquld carbon dioxide mustbe kept in drums under a pressure around 750 to 800 lbs. per

sq. in., and these drums are clumsy to handle and it is diiicult tocontrol the discharge of the gas therefrom. f

Increase in concentration .of carbon dioxide increases plant growthwithin certain limits, 'the increment of plant ,growth for any givenincrease in carbon dioxide concentration alling oil' as the total carbondioxide concentration rises above'a certain' op'timum amountuntil itbecomes unprofitable to increase the concentration any further. Carbondioxide `is f effective in promoting plant growth only in sunlight,plants being unable to assimilate it in the dark. The charging of thehothouse atmosphere with carbon dioxide should, therefore, be started inthe morning.

After a given charge of carbon dioxide has been liberated in the air inthe hothouse, its concentration tends to fall off, due to absorption ofycarbon dioxide by the foliage and by the moisture of the soil and,also, to diffusion into the air in the upper part of the hothouses,losses through ventilators, etc. As far as practicable the concentrationshould be maintained for a suitable length of time at or around thepoint of maximum eiiciency, i. e., the point at which increased cost ofcarbon dioxide balances increased value of the roducts of the hothouse.The discharge o carbon dioxide should most desirably/ be rapid at irstto bring the concentration up to the desired point and then slowythereafter to compensate for losses.

A satisfactory approximation to the above ideal condition is obtained bymy method by, allowing solid carbondioxide to evaporate in open toppedmetal containers'havin a comparatively large heat absorbing sur ace andsuiicient thickness to allow of ready flow of land early part of theafternoon it is allowed to taper off in the latter part of the daylighthours. a

One convenient arrangement for carrying out the invention is shown inthe accompanying drawing, wherein:

Fig. 1 is a diagrammatic vertical transvers section of a hothouseequippedwith means to supply method Fig. 2 is a section on the line 1;and

Fig. 3 is a vertical section through one of the containers for solidcarbon dioxide.

The containers 1 are of heavy metal construction, desirably, cast ironcups, provided with rings 3 or the like forattachment of wires 2 bywhich the cups are suspended from a suitable part vof the roofconstruction of the hothouse. As shown, the roof of the hothouse 4 isprovided with cross-stays 5 which form convenient means for su portingthe cups. Suspensionof the cups 1 fiom the roof is preferable to.supporting them by tripods or uprightsl on the benches 6 as the latterare thereby left clear of all obstructions. Further, when suspended, theheight of the carbon dioxide according to my cups above the foliage maybe adjusted more readily than in the case where rigid supports arerovided.

.A suita le size of cup is about 5 inches in diameter and 4 or 5 inchesor more in height with walls about 1A inch thick. The cups are toadvantage suspended 1 to 2 feet above the to "of thefoila e.. The cupsare desirably distri uted along t e benches 1n staggered arrangement andat such distances apart that there is one cup for about`each500 squarefeet of floor area. With this ratio between the number of cups and thefloor .area a suitable eharge of solid carbon dioxide for each cu isabout 11/2 lbs.

V at is claimed is:

1. Method of enriching the carbon dioxide content of the atmosphere inthe neighborhood of growing plants, which comprises supplying carbondioxide gas by allowing sohd carbon dioxide to vaporize underatmospheric pressure. in a container arranged above the tops of thefoliage.

2. Method of enriching the carbon dioxide content of the atmosphere intheneighborhood of growing plants, which comprises supplying carbondioxide gas at a gradually decreasing rate by allowing solid carbondioxide to vaporize in a container open to the atmosphere.

3. Method of enriching the carbon dioxide my hand.

content of the atmosphere in the neighborhood of growing plants, whichcomprises supplying carbon dioxide gas by allowing solid carbon dioxideto vaporize in a plurality of containers open to the atmosphere arrangedabove the soil in which the plants are growing and substantiallyuniformly separatedl from each other.

4. Apparatus for enriching the carbon dioxide content of the atmospherein the neighborhood of growing plants, comprising a plurality ofcontainers for solid carbon dioxide open to the atmosphere arrangedabove the soil in which the plants are growing and substantiallyuniformly separated vfrom each other, the ratio between the areaofhground treated to the number of containers being of the order ofmagnitude of one container for each 500square feet ofioor area.

5. Apparatus for enriching the carbon dioxide content of the atmospherein the neighborhood of growing plants, comprising a container for solidcarbon dioxide formed of metal of substantial thickness to allow readyflow of heat from all parts of the surface of such container to theparts of the latter in contact with the solid carbon dioxide.

6. The ymethod of enriching the carbon di'- oxide content of theatmosphere in the neighborhood of growing plants which com risesallowing solid carbon dioxide to vaporize in a container, the rateofvaporization being determined by thel rate of absorption of externalheat by the container and its contents.

In testimony whereof, I have hereunto set JOHN c. MINOR.v

